1. Field of the Invention
The present invention relates to semiconductor device manufacturing equipment. More particularly, the present invention relates to semiconductor device manufacturing equipment having a process chamber, and an exhaust system that evacuates the process chamber and exhausts gaseous products from the process chamber.
2. Description of the Related Art
A semiconductor device is generally fabricated in part by forming a thin film on a substrate, and selectively etching the thin film to form a desired specific pattern on the substrate. These main processes are carried out in a low pressure and high temperature process atmosphere maintained within a so-called process chamber. In particular, the substrate is supported within the process chamber. Then, a reactant gas is injected into the process chamber and an RF power is applied to excite the gas. As a result, a chemical reaction is facilitated that forms a specific thin film on the substrate or etches a thin film that is already present on the substrate. In addition, gaseous products are essentially created as a by-product of the chemical reaction.
As an example, a low pressure chemical vapor deposition (LPCVD) process facilitates a chemical reaction of Si2HCl2 and NH3 to form a thin film of Si3N4 on a substrate. The reaction creates NH4Cl as a gaseous by-product. The by-product remains gaseous in low pressure and high temperature conditions, but tends to transform into powder at a higher pressure and lower temperature.
In particular, a large amount of the gaseous by-product transforms into powder due to an increase in pressure and drop in temperature that occurs while the gaseous by-product is being exhausted from the process chamber by an exhaust system of the LPCVD equipment. The powder is highly adhesive. Therefore, it clings to an exhaust line or a vacuum pump of the exhaust system, thereby causing a drop in the power of the exhaust system.
Accordingly, a cooling trap has been conventionally provided in the exhaust line that connects the process chamber with the vacuum pump of the exhaust system. The cooling trap forcibly cools the gas to transform it into powder that adheres to the cooling trap. This aims to prevent any of the powder from entering or adhering to the vacuum pump.
FIG. 1 illustrates an arrangement in which a cooling trap is applied to conventional semiconductor device fabrication equipment.
As shown in FIG. 1, a cooling trap 4 is provided on an exhaust line 3 that connects a vacuum chamber 1, such as a process chamber, and a vacuum pump 2. The cooling trap 4 defines a passage through which a refrigerant, such as cool water, circulates to forcibly cool any exhaust gas passing through the cooling trap 4, with the aim of solidifying the exhaust gas into powder. Exhaust products solidified in the cooling trap 4 are highly adhesive. Thus, most of the solidified exhaust products cling to the sidewall of the cooling trap 4.
However, the conventional cooling trap 4 fails to transform all of the exhaust gas into a solid by-product. Thus, some of the exhaust gas is introduced into the vacuum chamber 2, where the gas solidifies. As a result, the performance of the exhaust system in exhausting the vacuum chamber 2 is degraded, and the PM (preventative maintenance) of the equipment must be preformed more frequently. This, in turn, lowers the yield and productivity of the fabricating process, and shortens the useful life of the vacuum pump 2.